1. Field of the Invention
The present invention relates to a data compressing method and a data compressing apparatus and in particular, to a CAD (Computer Aided Design) data compressing method and an apparatus thereof.
2. Description of the Prior Art
As semiconductor devices are being microscopically structured, the data amount of CAD data for drawing patterns of masks and reticles used for a lithographing process of a semiconductor fabrication is drastically increasing. When CAD data is created, a data amount compressing method using a feature that drawing patterns are repeated is used. However, even if CAD data is compressed, because the resultant data may be as large as several Gbytes, whereas the file size has an upper limit of 1 Gbytes to 4 Gbytes, conventional operating systems cannot handle such a huge the CAD data. Although a particular OS version may handle such a huge file, the huge file occupies a large disc space. Consequently, it is difficult to use many files of CAD data on the same disc. In addition, since the data amount of CAD data is large, it takes a long time to transmit a file of CAD data through a network as well as reading and writing it. Therefore, in addition to drawing a pattern, it takes a long time to prepare the drawing operation. Moreover, when defects of a mask and a reticle are inspected, such CAD data should be handled. Thus, the inspection time tends to become long. Consequently, the data amount of CAD data should be further reduced.
Fertman and Ashida of Sony Corp (JPA 9-128421) and Tsujimura of Fujitsu Limited (JPA 5-29188) disclose CAD data compressing methods. According to these methods, a repetitive pattern group is stored to a dedicated area of a file or a separate file. When such a repetitive pattern group is described, only the position thereof is referenced. As a result, the same pattern group can be prevented from being repetitively described. As a result, CAD data can be compressed at high compression ratio. In that case, a pattern group represents a set of rectangles and trapezoids that are basic figures of CAD data of masks and reticles. A similar, but not the same, technology has been used in a CAD format of a mask drawing apparatus of Nippon Denshi K.K. (JBX-7000 MV, JEOL 52 (V.2.1) format specification). Moreover, Nakajima and Oonuma of Sony Corp. (JPA 10-149378) disclose another CAD data compressing method. According to the CAD data compressing method, repetition information such as repetition intervals of a pattern group and the number of repetition times is stored to a dedicated area of a file or another file. When the pattern group is repeated, the repetition information is referenced. Thus, repetition information can be prevented from being redundantly described. As a result, the compression ratio of CAD data is improved.
However, such prior art references have disadvantages as follow:.
(1) Even if a part of basic figures in a pattern group is the same as a part of basic figures in another pattern group, the presence of such a common basic is not described. Thus, if a pattern group is slightly different from another pattern group, they are registered as different pattern groups with a list (see FIG. 1).
(2) There is no description as to how to handle a CAD data in which repetitive figures and non-repetitive figures co-exist.
(3) Although repetitive figures and repetitive pattern groups are registered with a list, if they are referenced only one time, information amount that represents the reference destination is additionally required (show in FIG. 2).
(4) If the number of repetition times of a repetitive figure is large, the information amount (the number of bits) that represents the number of repetition times becomes large. Thus, the number of bits exceeds a pre-allocated memory area. In contrast, if the pre-allocated memory area is too large, the compression effect will deteriorate. For example, if the number of repetition times of a repetitive pattern is 255 or less, the number of repetition times can be represented by 8 bits. However, even if the number of repetition times of a single repetitive pattern exceeds 255, the number of repetition times must be 9 bit or more.
(5) There is no description as to whether repeated is a single figure, a pattern group composed of a plurality of figures, or a pattern repeated once more. If each data structure is different from other data structure and pattern types are not identified, data are not correctly developed (shown in FIG. 3).
(6) According to the prior art references of Fertman, Ashida, Nakajima, and Oonuma, figures that constitute one pattern group are determined depending on whether repetition information of figures in a particular region is the same. However, when the number of figures contained in the region is very large, such a searching method requires a very long time.
(7) As a procedure for determining whether or not an inspected figure is repeated, Fertman and Ashida has proposed a technology for automatically extracting repetition information. However, the method using repetition information of CAD data disclosed by Nakajima and Oonuma is superior to the method disclosed by Fertman and Ashida in compressing time. However, even in the method disclosed by Nakajima and Oonuma, if the numbers of repetition times in the repetition information are different from one another, the repetition information is not compressed.
The present invention has been made to solve the aforementioned disadvantages.
According to a first aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating a component figure list; and generating data containing a pointer to a component figure in said component figure list for each of pattern groups.
The CAD data compressing method according to the first aspect of the present invention may further comprises the step of: if a single figure which is repeated is contained in said component figure list as a component figure, generating data containing a pointer to said component figure in said component figure list.
According to a second aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating data of a common pattern group composed of a plurality of basic figures common among a plurality of pattern groups; and generating data containing a pointer to said common pattern group for each of said plurality of pattern groups.
According to a third aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating a component figure list; and generating data containing a pointer to a component figure in said component figure list for each of isolated figures.
According to a fourth aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating a component figure list; and generating data containing a pointer to a component figure in said component figure list for each of isolated figures, each of pattern groups, and each of repetitive patterns.
According to a fifth aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating data of a first repetitive pattern whose number of repetition times is represented by a predetermined number of bits; and generating data of a second repetitive pattern containing a pointer to said data of said first repetitive pattern.
According to a sixth aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating data of a first repetitive pattern whose number of repetition times is represented by a first predetermined number of bits; generating data of a second repetitive pattern whose number of repetition times is represented by the first predetermined number of bits or a second predetermined number of bits; and generating data of a third repetitive pattern containing a pointer to said data of said first repetitive pattern and a pointer to said data of said second repetitive pattern.
According to a seventh aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating first data of a component figure, a single figure, a pattern group, or a repetitive pattern; and generating second data of a repetitive pattern containing a pointer to said first data and an identifier representing that said first data which is pointed by said pointer is of said component figure, said single figure, said pattern group, or said repetitive pattern.
According to a eighth aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating a set of first data of a component figure, a single figure, a pattern group, or a repetitive pattern and an identifier representing that said first data is of said component figure, said single figure, said pattern group, or said repetitive pattern; and generating second data of a repetitive pattern containing a pointer to the generated set.
According to a ninth aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating first data of a component figure, a single figure, a pattern group, or a repetitive pattern in one of designated regions for a component figure, a single figure, a pattern group, and a repetitive pattern; and generating second data of a repetitive pattern containing a pointer to said first generated data.
According to a tenth aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: generating first data of a component figure, a single figure, a pattern group, or a repetitive pattern in one of designated files for a component figure, a single figure, a pattern group, and a repetitive pattern; and generating data of a repetitive pattern containing a pointer to said first data.
According to a eleventh aspect of the present invention, there is provided a CAD data compressing method, comprising the steps of: selecting a repetitive pattern group from an input figure group corresponding to a user""s operation of an input device; and determining whether or not the selected pattern group is regularly repeated corresponding to CAD data which is an input compression source.
The CAD data compressing method according to the eleventh aspect of the present invention may further comprise the step of: selecting a region for determining whether or not the selected pattern group is regularly repeated corresponding to the user""s operation of the input device.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of the best mode embodiment thereof, as illustrated in the accompanying drawings.